For manufacturing an impression of the dental area, impression caps have become widely known in dentistry. They are used in the procedure for manufacturing a dental prosthesis, an imprint of a patient's dental positions becoming possible by means of these impression caps, which is true to nature and adapted to the position and direction.
Dental implants are used to replace lost, damaged or unaesthetic teeth. This is done by means of an artificial dental prosthesis in order to restore the chewing ability or the aesthetic appeal within a patient's mouth.
For manufacturing such a dental prosthesis, the dentist first places a dental implant in the jaw bone. After successful healing of the implant in the jaw bone, either an abutment or a different suitable cap, in the following called prosthodontist's adapter for simplification, is provisionally placed onto the implant for fastening an impression cap thereon which transfers the direction and position of a dental model to be manufactured at a later stage to the impression model. Then the impression cap is placed onto the implant with the abutment or prosthodontist's adapter on top of it, and it is pressed onto the patient's jaw by means of a mold filled generally with a fast-setting impression compound (e.g. elastomers, silicone) for obtaining an imprint of the patient's teeth which is true to nature and geometrically correct.
During this process, the impression cap remains within the impression compound and is withdrawn from the jaw, together with the mold, after the impression compound has set. The plastic model created in this manner is used in the dental laboratory to precisely model the jaw and to produce an individual dental model. This conveying of the geometrical situation in the jaw onto a dental model, however, is extremely difficult, especially if the denture is positioned in the visible area, e.g. in the area of the front teeth, where aesthetic considerations are important. Minor deviations of the geometry, e.g. due to vibrations during the setting process during imprinting, have negative effects on the prosthodontist's mold to be produced and thus also on the dental prosthesis. The impression produced by the dentist is given to the prosthodontist as a base for manufacturing a plaster model of the jaw bone. In the laboratory, the prosthodontist places a provisional implant, in the following called prosthodontist's implant, having a suitable placed-on abutment or prosthodontist's adapter, onto the impression model with the impression cap located in it, which prosthodontist's implant is suited for modeling the implant positioned into the jaw and the dental prosthesis to be modeled on top of it. Thus, the prosthodontist's implant has the same position within the impression model as the implant placed into the patient's jaw bone. The geometrical relations within the patient's jaw can be modeled very precisely in this manner. Then the impression with the impression cap enclosed in it and the assembly of prosthodontist's implant and abutment on top of it is grouted with a plaster substance. After successful setting of the plaster substance, the impression mask is removed, and a complete plaster model of the patient's jaw with the prosthodontist's implant cast in is provided for further denture manufacturing.
Impression caps are known in various embodiments which have different shapes depending on the task of the dental model to be produced. Thus, impression caps adapted to the shape of the abutment are known which, however, have the disadvantage that the dentist must have a large number of impression caps in store for various geometries of the occlusal part of an abutment, in order to guarantee the precise adaptation to the abutment, since in case of exceedingly large clearances between the inner surface of the impression cap and the outer surface of the abutment's occlusal part, shifts of the impression cap can take place.
Also, impression caps with different fastening methods are known, such as impression caps which are screwed on or plugged on by means of a clamping device. Clamping-type impression caps generally have flexible portions on the side facing the implant, which portions can clamp the dental implant; however, they are insufficiently secured against torsions since the clamping only acts on the collar area of the abutment, and therefore they easily slide off in the clamp connection area. Such an impression cap is e.g. known from EP 0 680 732 B1.
Furthermore, an impression cap is known from U.S. Pat. No. 6,382,977 B1, which impression cap is provided with flexible thin-walled portions at its proximal end, which portions snappingly engage the implant's interior. The proximal end of the impression cap also has an adjustment recess or an adjustment hub for assuming a specific position in the implant's interior.
During manufacturing of such impression caps, it has been shown in practice that the production of an impression cap with the flexible portions provided on it for clamping or snapping onto the implant presents substantial problems during injection molding, since they must be manufactured with great precision. Due to this required precision, these injection-molding model forms are costly to produce; and in addition, it has been shown that manufacturing of these thin-walled structures is extremely difficult.